Fernando Leyton

SCATTER AND STAFF DOSE LEVELS IN PAEDIATRIC INTERVENTIONAL CARDIOLOGY: A MULTICENTRE STUDY

Interventional cardiology procedures usually imply high doses to the staff, as paediatric cardiologists need to stay closer to the patient than during adult procedures. Also, biplane systems are used that imply an additional source of staff doses. The objective of this paper is to measure scatter doses in four X-ray systems, using polymethyl methacrylate phantoms with thicknesses ranging from 4 to 16 cm to simulate paediatric patients, for the different acquisition modes. Scatter dose rates measured at the position of cardiologists eyes ranged from 0.8 to 12 mSv h(-1), and about twice the above values at lower extremities, as a linear function of the surface air kerma at the phantom, keeping the irradiated area constant. Therefore, the respective personal dose equivalent for the lens of the eyes may be around 0.5 and 1 mSv throughout the procedure, if additional protection is not used. Simultaneous cine acquisition in biplane systems yielded scatter doses to cardiologists, increased by factors from 5 to 21, compared with a single C-arm acquisition case and depending on geometry. Knowledge of scatter doses for different operation modes, patient thicknesses and the biplane operation should help paediatric cardiologists to adopt conservative attitudes in respect of their occupational radiation risks.

Radiation protection in pediatric interventional cardiology: An IAEA PILOT program in Latin America.

The aim of this work is to present a methodology and some initial results for a pilot program on radiation protection (RP) in pediatric interventional cardiology under the auspices of the International Atomic Energy Agency. The starting point of the program was a workshop involving several pediatric cardiologists leading this specialty in 11 Latin American countries. The workshop included a pilot RP training course and additional sessions during which the objectives of the program and the methodology to collect and process data on patient and staff radiation doses were discussed. Special attention was dedicated to agree on a common quality control (QC) protocol for the x-ray and imaging systems used in the different catheterization laboratories. The preliminary data showed that only 64% of the cardiologists used their personal dosimeters regularly and that only 36% were aware of their personal dose values. The data on pediatric interventional activity were collected from 10 centers from nine different countries. A total of 2,429 procedures (50% diagnostic and 50% therapeutic) were carried out during 2009 in these centers. Patient dose data were available in only a few centers and were not analyzed on a regular basis in any of the catheterization laboratories involved. Plans were developed for a basic QC protocol of the x-ray systems and construction of a Latin American database on pediatric cardiology with patient and staff dose values with the idea in mind of obtaining distributions of these dose values before promoting several optimization strategies.

Pilot program on patient dosimetry in pediatric interventional cardiology in Chile

PURPOSE The aim of this study was to present the results of a pilot program on patient dosimetry carried out in Chile during the last 5 yr, using a biplane x-ray angiography system settled for pediatrics. This research was conducted in Latin America under the auspices of the International Atomic Energy Agency (IAEA) supporting programs on radiological protection (RP) of patients. METHODS Patient age, gender, weight, height, number of cine series, total number of cine frames, fluoroscopy time, and two dosimetric quantities [air kerma-area product (P(ka)) and cumulative dose (CD) at the patient entrance reference point] were recorded for each procedure. RESULTS The study includes 544 patients grouped into four age groups. The distributions by age group were 150 for <1 yr; 203 for 1 to <5 yr; 97 for 5 to <10 yr; and 94 for 10 to <16 yr. Median values of P(ka) and CD for the four age groups were 0.94, 1.46, 2.13, and 5.03 Gy cm(2) and 23.9, 26.8, 33.5, and 51.6 mGy, respectively. No significant statistical differences were found between diagnostic and therapeutic procedures. A moderate correlation (r = 0.64) was seen between P(ka) and patient weight. CONCLUSIONS The dose values reported in this paper were lower than those published in the previous work for the same age groups as a result of the optimization actions carried out by cardiologists and medical physicists with the support of the IAEA. Methodology and results will be used as a starting point for a wider survey in Chile and Latin America with the goal to obtain regional diagnostic reference levels as recently recommended by the International Commission on Radiological Protection for interventional procedures.

Radiation dose and image quality for paediatric interventional cardiology systems. A national survey in Chile

Radiation dose and image quality for paediatric protocols in all five X-ray fluoroscopy systems used for interventional cardiology procedures existing in Chile have been evaluated. Entrance surface air kerma (ESAK) and image quality using a test object (TO) and polymethyl methacrylate (PMMA) phantoms have been measured for the typical paediatric patient thicknesses (4-16 cm of PMMA). Images from fluoroscopy (low (FL), medium and high) and cine (CI) modes have been archived in DICOM format. Signal-to-noise ratio (SNR), figure of merit (FOM) and high-contrast spatial resolution (HCSR) have been computed from the images. The ratio between the maximum and the minimum value of ESAK per frame for a given fluoroscopy mode between the five systems ranges from 2 to 5 and from 14 to 38 for CI mode. SNR, FOM and HCSR showed a great variability for the different acquisition modes (AMs) and PMMA thickness. In the near future, it is urgent to upgrade Chilean legislation on radiation protection to incorporate quality assurance programmes that will allow us to evaluate and optimise the X-ray systems used in medical applications. Increments in doses per frame when increasing phantom thickness and when used CI runs instead of FL runs can be considered by the cardiologist in the good management of patient dose and allow them to select the best imaging AM during clinical procedures.

Radiation dose and image quality for adult interventional cardiology in Chile: a national survey

The aim of this work was to investigate the differences in dose settings and image quality among 10 X-ray systems used for interventional cardiology in Chile. Entrance surface air kerma (ESAK) was measured on a phantom of 20 cm thickness of polymethyl methacrylate slabs. Image quality was evaluated using DICOM images of a test object Leeds TOR 18-FG for cine mode acquisition, through the numerical parameters signal-to-noise ratio (SNR), high-contrast spatial resolution (HCSR) and figure of merit. ESAK rate values for fluoroscopy modes ranged between 7.1 and 121.7 mGy min(-1). For cine mode, ESAK values per frame ranged from 63 to 400 µGy fr(-1). SNR and HCSR parameters for cine mode varied from 4.8 to 8.6 and 0.4 to 10, respectively. FOM values resulted from 6.9 to 64.5 among the different X-ray systems. Results show important differences between systems and point out the need to launch an optimisation programme.

LATIN AMERICAN DOSE SURVEY RESULTS IN MAMMOGRAPHY STUDIES UNDER IAEA PROGRAMME: RADIOLOGICAL PROTECTION OF PATIENTS IN MEDICAL EXPOSURES (TSA3)

Latin American countries (Argentina, Brazil, Chile, Costa Rica, Cuba, Ecuador, El Salvador, Guatemala, Mexico, Nicaragua, Paraguay, Uruguay and Venezuela) working under the International Atomic Energy Agency (IAEA) Technical Cooperation Programme: TSA3 Radiological Protection of Patients in Medical Exposures have joined efforts in the optimisation of radiation protection in mammography practice. Through surveys of patient doses, the region has a unique database of diagnostic reference levels for analogue and digital equipment that will direct future optimisation activities towards the early detection of breast cancer among asymptomatic women. During RLA9/057 (2007-09) 24 institutions participated with analogue equipment in a dose survey. Regional training on methodology and measurement equipment was addressed in May 2007. The mean glandular dose (DG) was estimated using the incident kerma in air and relevant conversion coefficients for both projections craneo caudal and mediolateral oblique (CC and MLO). For Phase 2, RLA9/067 (2010-11), it was decided to include also digital systems in order to see their impact in future dose optimisation activities. Any new country that joined the project received training in the activities through IAEA expert missions. Twenty-nine new institutions participated (9 analogue and 20 digital equipment). A total of 2262 patient doses were collected during this study and from them D(G) (mGy) for both projections were estimated for each institution and country. Regional results (75 percentile in mGy) show for CC and MLO views, respectively: RLA9/057 (analogue) 2.63 and 3.17; RLA/067: 2.57 and 3.15 (analogue) and 2.69 and 2.90 (digital). Regarding only digital equipment for CC and MLO, respectively, computed radiography systems showed 2.59 and 2.78 and direct digital radiography (DDR) systems 2.78 and 3.04. Based on the IAEA Basic Safety Standard (BSS) reference dose (3 mGy), it can be observed that there is enough room to start optimisation processes in Latin America (LA); several countries or even particular institutions have values much higher than the 3 mGy. The main issues to address are lack of well-established quality assurance programmes for mammography, not enough medical physicists with training in mammography, an increase in patient doses with the introduction of digital equipment and to create awareness on radiation risk and optimisation strategies.

Riscos da Radiação X e a Importância da Proteção Radiológica na Cardiologia Intervencionista: Uma Revisão Sistemática

AbSTRACT Radiation Risks and the Importance of Radiological Protection in Interventional Cardiology: A Systematic Review We discuss some aspects related to the legal framework, international recommendations and training programs on radiological protection; image quality and equipment; the biological effects and risks of ionizing radiation; lesions in patients and operators; patient’s reference levels; occupational dose limit and preventive actions. The use of ionizing radiation involves risks that are justified in diagnostic and therapeutic procedures. The awareness and knowledge of these risks minimizes the damage, optimizing the quality of images and safe use of ionizing radiation. There is evidence of radiation-induced cataracts in individuals who work in catheterization laboratories. Several studies suggest there may be a significant risk of lens opacity, if radiological protection devices are not properly used. Additionally, these interventional procedures are performed in Latin America, usually by medical specialists in collaboration with nurses, technologists and technicians, who often do not have adequate training in radiological protection.

Radiation Risks and the Importance of Radiological Protection in Interventional Cardiology: A Systematic Review

ABSTRACT We discuss some aspects related to the legal framework, international recommendations and training programs on radiological protection; image quality and equipment; the biological effects and risks of ionizing radiation; lesions in patients and operators; patient’s reference levels; occupational dose limit and preventive actions. The use of ionizing radiation involves risks that are justified in diagnostic and therapeutic procedures. The awareness and knowledge of these risks minimizes the damage, optimizing the quality of images and safe use of ionizing radiation. There is evidence of radiation induced cataracts in individuals who work in catheterization laboratories. Several studies suggest there may be a significant risk of lens opacity, if radiological protection devices are not properly used. Additionally, these interventional procedures are performed in Latin America, usually by medical specialists in collaboration with nurses, technologists and technicians, who often do not have adequate training in radiological protection.

Influence of the exposure time in the area monitors at radiodiagnostic

Area monitoring ensures radiation exposure at an acceptable level, which must be lower than the legal limit. Experimental measurements were taken in an ionizing radiation calibration laboratory. The specified reference radiation to radiation protection N80 was used. Five area monitors were used. The ranges of dose rate inaccuracy measured in rate mode for times ≤ 2 and ≥ 3s were from 10 to 48% and from 1 to 15%, respectively. The inaccuracy ranges measured in integrated mode for times ≤ 2 and ≥ 3s were from 4 to 8% and from 0 to 22%, respectively.

Magnitudes y unidades para dosimetría a pacientes en radiodiagnóstico e intervencionismo

Debido a que los procedimientos de radiodiagnostico e intervencionismo representan una de las principales fuentes de irradiacion a la poblacion por radiaciones ionizantes, se vuelve prioritario conocer las magnitudes y unidades que dan cuenta de la dosimetria a los pacientes. Existen innumerables documentos y recomendaciones internacionales sobre nombres, conceptos, definiciones y campos de aplicacion para diversas magnitudes y unidades utilizadas en la dosimetria de pacientes en procedimientos de radiodiagnostico e intervencionismo. Sin embargo, la legislacion nacional no se encuentra actualizada en este sentido y no contempla en ninguno de sus documentos, un glosario actualizado que permita encontrar en forma rapida y precisa este tipo de informacion. Por lo anterior, este trabajo de revision presenta de manera didactica y en un lenguaje sencillo, las principales magnitudes y unidades que se deben utilizar en la dosimetria de pacientes sometidos a procedimientos de radiodiagnostico e intervencionismo.